that's it? all i need is a bellmouth that opens up 1/4 inch on either side? i can probably bring the shims down pretty close come to think of it. unfortunatly i can not increase my prop diameter because this is one of the precious few propeller blades that come in matching counter rotating sets or are available. the draganflyer blades are the only ones that are 11" (1" larger than mine) but they are made for spinning at 800 rpm not 4500 rpm and even at 3600 rpm they would go into negative pitch, even though i stiffened them and such. i dont really have any propeller options.[] also, about how long do you think the exit duct should be? and about how much static thrust do you guys think i should gain permotor?